Imaging devices (e.g., thermal imagers such as thermal cameras or visible light images such as visible light cameras) typically include a plurality of sensors arranged in rows and columns of pixels. Images (e.g., image frames) captured by the sensors often suffer from various types of noise. For example, fixed pattern noise (FPN) may appear in the captured images and may persist in a pattern that remains relatively constant over multiple images.
FPN is conventionally detected using an opaque shutter implemented as a substantially uniform black body. The opaque shutter may be temporarily introduced in front of the sensors which capture images of the opaque shutter. FPN can be identified by the deviations from an expected uniform black body response in the captured images. Following such capture, the opaque shutter is moved out of the sensors' field of view. These FPN detections may be repeated, as FPN can slowly change over time in response to external and internal thermal conditions.
Unfortunately, this conventional approach requires the sensors to be blocked from viewing an external scene while the opaque shutter is in place. As a result, the sensors are prevented from capturing any images of the scene during FPN detection. Moreover, these disruptions repeat each time a new FPN detection occurs. As a result, there may be multiple time periods during which no scene information is available to the imager. This is problematic, especially for security and mission critical applications where even brief scene interruptions may result in important image data being lost.
Although some conventional shutters are capable of being quickly deployed, such implementations typically require expensive and heavy components to achieve rapid movement. Moreover, scene information will still be interrupted for periods of time while the shutter is in place.